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Year 2010 X ~ N(25.4, 1.5) μ = 25.4 σ = 1.5 10 Example Random Variable X = Age at first birth POPULATION Question: What proportion of the population had their first child before the age of 27.2 years old? P(X < 27.2) = ? 27.2

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11 Example Random Variable X = Age at first birth POPULATION Question: What proportion of the population had their first child before the age of 27.2 years old? P(X < 27.2) = ? Year 2010 X ~ N(25.4, 1.5) σ = 1.5 μ =μ = 33 The x-score = 27.2 must first be transformed to a corresponding z-score. μ = 25.4 27.2